Counterbalance touch control

ABSTRACT

The key depression touch of a key-actuated business machine is controlled by adjusting the position of a spring bail which simultaneously controls the tension of all the key lever springs. A manually positioned control member with attendant linkages positions the spring bail and simultaneously adjusts the tension of counterbalancing spring means to minimize the unbalanced spring forces acting on the spring bail and the entire touch control system at all touch settings of the touch control apparatus.

United States Patent [191 Diamond [.11 3,823,806 7 [451 July 16,1974

[ COUNTERBALANCE TOUCH CONTROL [75] Inventor: Herrick R. Diamond, Homer,N.Y.

[73] I Assignee: SCM (Zorporation, New York, N.Y. [22] Filed: Jan. 8,1973 [21] Appl. No.: 321,611

[52] US. Cl 197/33, 197/17 [51] Int. Cl B4lj 7/26 [58] Field of Search197/33, 27, 17, 98

[56] References Cited UNITED STATES PATENTS 1,741,690 12/1929 Ely 197/332,098,285 11/1937 Gabrielson et al..... 197/33 2,148,690 2/1939 Going197/33 2,148,877 2/1939 Rauscher 197/33 2,169,349 8/1939 Myers 197/332,226,924 12/1940 Dobson 197/33 2,567,943 9/1951 Kl0ski.....' 197/332,624,439 1/1953 Zeamer 197/33 2,660,285 11/1953 Kennedy, Jr 197/332,682,944 7/1954 Schremp 197/33 3,409,111 11/1968 Cappotto 197/33Primary Examiner-Robert E. Pulfrey Assistant Examiner-E. H. EickholtAttorney, Agent, or Firm-Kenneth W. Greb; Milton M. Wolson, Esq,

[ 5 7] ABSTRACT The key depression touch of a key-actuated businessmachine is controlled by adjusting the position of a spring bail whichsimultaneously controls the tension of all the key lever springs. Amanually positioned control member with attendant linkages positions thespring bail and simultaneously adjusts the tension of counte'rbalancingspring means to minimize the unbalanced spring forces acting on thespring bail and the entire touch control systemat all touch settings ofthe touch control apparatus.

7 Claims, 5 Drawing Figures PATENTEB JUL 1 5 m4 SHEU 1 Hi2COUNTERBALANCE TOUCH CONTROL BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to key actuated business machines and,more particularly, to apparatus for controlling the key depression touchof key-actuated business machines.

2. Description of the Prior Art Control of the effort, or touch,required to depress the key levers in key lever actuated businessmachines isvery important if operating personnel are to achieve maximumutilization of the machines. However, because most business machineshave intricate key lever mechanisms, it is difficult to effectivelycontrol the key lever depression touch of these machines. For example,some business machines have'utilized spearately adjustablespring'devices connected to each key lever to adjust the depressiontouch for each individual key. Needless to say, though these individualspring adjustment mechanisms insured touch control for each individualkey, they provide many problems, particularly with regard to uniformityof the depression touch between the various keys in the keyboard. Inthis type of machine, it was often necessary to adjust the touch controlfor a few keys in order to bring the depression touch of the keys intouniformity. Because of the numerous adjustments, the problems presentedwith maintenance of the machine were substantial.

A second approach of the control of the key depression touch ofkey-actuated business machines has been to connect each of the keylevers to a spring bailby means of key lever springs and then adjust theposition of the spring bail to simultaneously adjust the tension of allthe key lever springs, thereby simultaneously adjusting the forcesnecessary to depress the individual keys. Although this approach appearssimple, it has proved less than successful in many instances because ofthe substantial forces required to control the spring bail and therebyadjust and maintain the tension of all the key lever springssimultaneously.

The individual key lever springs act together to exert a substantialforce on the spring bail. Therefore, the

mechanism which positions the spring bail must provide forces sufficientto counteract the combined key lever spring forces. This has been donein the past by a manually positioned control member. However, becausethe combined spring lever forces acting on the spring bail are so muchgreater in settings which require heavy touch effort than in settingswhich require low touch effort, it is relatively difficult to positionthe control member in the settings for high touch effort. Further, touchcontrol adjusting devices have a tendency to drift from heavy toucheffort settings to light touch settings because of the combinedunbalance force of the key lever springs.

In order to prevent this tendency to drift out of position, many of thetouch control apparatuses use detent devices in which the control leverfor selecting the touch control value is held in predetermined positionsby means of detents to provide established touch control settings. Thesedetent devices are not without disadvantages, and do not completelysolve the problem of touch control selection. Most of the key-actuatedbusiness machines, such as typewriters or adding machines, are subjectto vibration and impact laods which .tend to jar the detent device outof its setting. This is especially so in the newer electric typewritersand adding machines. Further, the detent device requires a separatenotch for each settingof the control member, thereby limiting the numberof settings usually provided. Also, because the unbalanced spring forceson the touch control device substantially increase as the touch settingis increased, it is more difficult to position the control member in theproper detent notch in the higher touch effort settings than in thelower touch effort settings.

Attempts have been made to overcome the problems of manually positioningthe control member of the touch control apparatus by increasing themechanical advantage of the manually positioned control member inrelation to the spring bail. However, this approach usually involvesapparatuses having relatively long linkages and levers such as thatshown in US. Pat. No. 3,409,111 issued to D. Cappotto on Nov. 5, 1968and in a Pat. No. 2,098,285 issued to C. Gabrielson et al. on Nov. 9,1937, which cannot be conveniently positioned and actuated within theconfines of existing business machine housings.

BRIEF SUMMARY OF THE INVENTION To overcome the problems inherent in theprior art,

the present invention sets forth apparatus to control the key depressiontouch of a key-actuated business machineby adjusting the position of aspring bail which simultaneously controls the tension of all the keylever springs. A manually actuated control member, with attendantlinkages, positions the spring bail and simultaneously adjuststhetension of counterbalancing spring means, to minimize the unbalancedspring forces acting on the spring bail, and the entire keydepressiontouch control apparatus.

Accordingly, it is an object of the present invention to provideapparatus for controlling the key depression touch of key-actuatedbusiness machines which does not require application of large unbalancedspring forces in order to control the key depression touch.

Another object of the present invention is to provide apparatus forcontrolling the key depression touch of key-actuated business machineswhich can be adjusted from one touch setting to another withoutsubstantially changing the unbalanced forces acting on the touch controlapparatus.

It is a further object of thepresent invention to pro-' vide apparatusfor controlling the key depression touch of key-actuated businessmachines which does not require a variation of the forces exerted on themanually positioned control member when adjusting the key depressiontouch from one setting to another.

Still another object of the present invention is to provide apparatusfor controlling the key depression touch of key-actuated businessmachines which does not tend to drift from one setting to anothersetting during operation of the business machine.

It is an additional object of the present invention to provide apparatusfor controlling the key depression touch of key-actuated businessmachines which provides a counterbalance spring means having a springwhich increases in pulling force as it slightly decreases in length.

Another object of the present invention is to provide apparatus forcontrolling the key depression touch of key-actuated business machineswhich is highly sensitive and provides an infinite number of touchsettings.

A further object of the present invention is to provide apparatus forcontrolling the key depression touch of key-actuated business machineswhich adjusts all keys simultaneously and uniformly.

It is still another object of the present invention to provide apparatusfor controlling the key depression touch of key-actuated businessmachines which provides a substantial mechanical advantage to allow easymanual positioning of the control member when adjusting the keydepression touch setting.

An additional object of the present invention is to provide apparatusfor controlling the key depression touch of key-actuated businessmachines which is relatively compact and easily mounted within thehousing of normal business machines.

It is another object of the present invention to provide apparatus forcontrolling the key depression touch of key-actuated business machineswhich has relatively few parts, is relatively cheap to manufacture, andrelatively durable in operation.

A further object of the present invention is to provide apparatus forcontrolling the key depression touch of key-actuated business machineswhich provides an extremely large mechanical advantage for the manuallypositioned control member so that unbalanced forces in the touch controlsystem do not have a tendency to change the setting of the system.

Other objects and advantages will be apparent from the followingdescription of an embodiment of the inpointed out hereinafter inconnection with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS ratus shown in FIGS. 1 and 2.

FIG. 4 is a perspective view of the touch control apparatus shown in theminimum touch effort position.

FIG. 5 is a view of the touch control mechanism shown in the maximumtouch effort position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the invention willhereinafter be described in connection with a' typewriter, it will beunderstood that the invention can be applied to a wide variety ofkey-actuated business machines other than typewriters.

Referring to FIG. 1, a typewriter, generally indicated at 10, has aframe 12, and a keyboard, generally indicated at 14, comprising aplurality of key buttons 16, each of which is connected to a key lever18, which, through various linkages, actuates a typebar (not shown), asis well known in the typewriter art. As shown in FIGS. 2 through 5, eachkey lever 18 is connected by means of a key lever'spring 20 to a springbail 22 fixed to a shaft 24 which is rotatably mounted to the left andright walls 26 and 28 respectively of frame 12. At the left end of bailshaft 24, extending beyond left vention, and the novel features will beparticularly wall 26, is fixedly positioned a spring lever 30 whichrotates with shaft 24. A counterbalancing spring 34 is connected at oneof its ends to a finger 32 on spring lever 30 and is connected at itsother end to finger 36 extending 'from the left wall 26 of frame 12.

On the right end of bail shaft 24, extending beyond right wall 28 offrame 12, is fixedly connected a bell crank 38 which rotates with bailshaft 24. A second counterbalance spring 42 is connected at one of itsends to a finger 40 on bell crank 38 and is connected to a finger 44extending from right wall 28 of frame 12. This assembly of spring 34 andspring 42 positions their respective lines of force substantially acrossthe axis of shaft 24 as shown in FIGS. 2 through 4. This assembly alsopositions the spring 34 and the spring 42 in a sideby-side relationshipwith the row of springs 20 thus providing a compact and efficientcounter-balance spring system. The bell crank 38 also includes an arm 46to which is connected the swing arm 50 of a pivot member 52 by means ofa translation link 48. Pivot member 52 is pivotally mounted ma leg54.extending from the right wall'28 of frame 12 by means of a pivot pin56 which extends through the upper and lower arms 58 and 60 of pivotmember 52. A cam pin 62 extends upwardly from upper arm 58 ofpivotmember 52 to control the movement of the swing arm 50, as will nowbe described.

Pivot member 52 is controlled by manually positioning a control knob 64rotatably mounted on the leg 54 of frame 12 A retaining pin 66 has alarge cylindrical shank 68 extending through cylindrical passage 76 inthe hub of the control knob and a smaller threaded end 70 which engagespassage 72 in leg 54. The control knob 64 has'a cam groove 74 in theunderside of the knob which spirals outwardly from the centralcylindrical passage 76 of the knob, about which the knob rotates. Campin 62 fits within the cam groove 74 so that rotation of the controlknob in the counterclockwise direction, shown by the arrow in FIG. 2,will tend to make cam pin 62 move away from the retaining pin 66,causing pivot member 52, including swing arm 50, to move in theclockwise direction, toward the position shown in'FIG. 4.Similarly,clockwise rotation of the control knob 64 will tend to movecam pin 62 closer to the retaining pin 66 and, therefore, urge the pivotmember 52 with swing arm 50 around pivot pin 56 in the counterclockwisedirection toward the position shown in FIG. 5.

A brake member 78 is placed between the leg 54 of frame 12 and thebottom of the control knob 64 to prevent random movement of the controlknob. The brake member includes four contact feet 80 which are raisedabove and connected to the central position of the brake member by bentarms 81. The brake member is held fixed in place by the shoulder 69 ofthe retaining pin 66 formed between the shank 68 and the threaded end70' of the retaining pin. Threaded end 70passes through the retainingpin passage 82 of the brake member. Additionally, an anchoring tab 84extends from the central portion of brake member 78 and fits into ananchor slot 86 on leg 54 of the frame12. The contact feet 80 of thebrake rub against the underside 88 of the control knob which forms abrake surface for the control knob, so that the control knob will notdrift after it is set at a particular position.

OPERATION The effort required to depress a key lever is controlled bymanually positioning the control knob which will position the springbail to adjust the tension of the key lever springs which, in turn,determine the amount of force necessary to depress the key leverbuttons.

As shown in FIG. 4, when the control knob 64 is rotatedcounterclockwise, the cam pin 62 will move in helical cam groove 74 ofthe control knob away from retaining pin 66 of the control knob so thatthe swing arm 50 of pivot member 52 will rotate clockwise, therebypulling translation link 48 to the left to cause bell crank 38 to rotatecounterclockwise. The counterclockwise rotation of bell crank 38 willcause the bell of spring bail 22 to move upward toward key levers 18,thereby allowing each key lever spring 20 to contract to a lowerstressed condition. Thus, the key lever springs will exert a relativelylight force on the key levers so that the amount of force or touchrequired to depress the key buttons on the key lever will be at aminimum.

When the spring bail 22 is in the raised position, the finger 40 of bellcrank 38 is positioned with respect to finger 44 of right wall 28 offrame 12, so that counterbalance spring 42 connecting fingers-40 and 44is ex tended to a maximum position and substantially crosses the axis ofshaft 24. Similarly, finger 32 of spring lever on the left end of bailshaft 24 is positioned so that the counterbalance spring 34 connectingspring lever finger 32 with finger 36 of left wall 26 of the frame isalso at the maximum extension and substantially crosses the axis ofshaft 24. Accordingly, the forces of both counterbalance springs 34 and42 exert torques on spring bail shaft 24 which oppose the torquesexerted on the spring bail shaft 24 by the key lever springs 20.

To move the touch control system from a setting requiring lightdepression pressure to one requiring heavier pressure, the control knob64 is rotated in the clockwise direction (opposite the arrow in FIG. 2),so that the cam pin 62 will follow the helical cam groove 74 ofthecontrol knob 64 toward the center of the control knob, thereby movingpivot member 52 counterclockwise and swing arm 50 toward the right,which motion is, in turn, translated through translation link 48 to arm46 of hell crank 38 to rotate the bell crank 38 in the clockwisedirection. If control knob 64 were turned the full range of travelclockwise, arm 46 of bell crank 38 would move upward to the verticalposition shown in FIG. 5, and fingers 32 of spring lever 30 and 40 ofbell crank 38 would move closer to the frame to slightly shortencounterbalance springs 34 and 42. Having one end of spring 34 connectedto finger 32 of spring lever 30 and one end of spring 42 connected tofinger 40 of bellcrank 38, the pulling force of the spring 34 and 42increases as the ends of the springs 34 and 42 are carried away from theaxis of shaft 24 thereby compensating for the decreasing pulling forceas the springs 34 and 42 slightly shorten. ln the position shown in FIG.5, the spring ball 22 has been moved to a nearly vertical positionextending the key lever springs 20, increasing the tension of thesprings, and, therefore, increasing the force required to depress thekey levers. While the extended key lever springs 20 exert acounterclockwise torque on the bail shaft 24,

the left and right counterbalance springs 34 and 42, though shortened,still exerted a counterbalancing clockwise torque on the bail shaft 24,which balances the torque exerted by the key lever springs 20.Accordingly, it can be seen that no matter what positions the springbail 22 is placed in or being moved to by the control knob, there willbe counterbalancing forces exerted on the bail shaft 24, so that theunbalanced force exerted on the bail shaft 24 will be of a relativelysmall nature.

The counterbalance apparatus of the invention possesses many advantages.For example, the apparatus provides great sensitivity of adjustmentbecause the helical cam in the control knob requires a largedisplacement to adjust the touch control over its full range.

Similarly, the use of a helical cam groove in the rotatable control knoboffers an extremely high mechanical advantage in positioning the springbail, so that a minimum of force is necessary on the part of theoperator of the machine to adjust the control knob. Additionally,because of the high mechanical advantage involved, the net forces whichare fed back from the spring bail shaft to the control knob through thetouch control apparatus are relatively small and can easily be handledby the brake mechanism described without the necessity for detents orother fixed stops in the control range. Therefore, the system will nothave a tendency to drift from one position to another, but will tend tobe more stable and not require continuous adjustment, as has heretoforebeen the case with many touch control systems. Since no detents arenecessary to hold the control knob, an infinite number of settings forthe control knob will be available to the operator. a

It should also be noted that the apparatus has relatively few movingparts which require a minimum of adjustment to insure proper operation.Therefore, the apparatus should be relatively inexpensive to manufactureand be highly durable in service. v

It will be understood that various changes in the details, materials andarrangements of parts which have been herein described and illustratedin order to explain the nature of the invention may be made by thoseskilled in the art within the principle and scope of the invention, asexpressed in the appended claims.

What is claimed is:

1. An apparatus for adjusting the depression touch effort of key leversin a key lever actuated business machine, comprising:

a spring bail chine; key lever spring means operatively connected toeach key lever and to said spring bail effecting the depression. toucheffort of the key lever and urging said spring bail to move in a givendirection; counterbalance spring means operatively connected to saidspring bail for urging said spring bail to.

move in a direction opposite to said given direction of said key leverspring means, said counterbalance spring means includes a shaft, amember extending substantially radially from said shaft, and a springconnected to said member, said spring being operable by said member formoving said spring from a position substantially crossing the axis ofsaid shaft to a position away from the axis of said shaft to increasethe pulling force of said spring'as said spring decreases in length; and

movably mounted in the business macontrol means operatively connected tosaid spring bail and to said counterbalance spring means for adjustingsaid k'ey lever spring means thereby effecting the depression toucheffort of the key levers and for simultaneously adjusting saidcounterbalance spring means to minimize variations of the spring forcesacting on said control means.

2. The apparatus as defined in claim 1 wherein said control meansincludes a linkage connected to said counterbalance spring means formoving said spring bail to adjust the depression touch effort of the keylevers through said counterbalance spring means.

3. The apparatus as defined in claim 1 wherein said spring bail isrigidly connected to said shaft of said counterbalance spring means andsaid spring bail is moved by said shaft for adjusting the depressiontouch effort of the key levers.

4. The apparatus as defined in claim 1 wherein said spring bail isrigidly connected to said shaft of said counterbalance spring means,said member of said counterbalance spring means is rigidly connected tosaid shaft and said control means includes a linkage connected to saidmember and operable to move said pr'ession touch effort of the keylevers.

5. The apparatus as defined in claim 1 wherein said control meansincludes a brake means to resist movement of said control means, saidcounterbalance spring means and said spring bail from any adjustedposition of said control means.

6. The apparatus as defined in claim 5 wherein said.

control means includes a control knob and said brake means includes abrake member contacting said control knob to prevent said control knobfrom drifting from adjusted positions.

7. The apparatus as defined in claim 1 wherein said control meansincludes:

a control knob rotatably mounted in the business machine; a cam surfacein said control knob; and pivot means in contact with said cam surfaceand operatively connected to said spring bail to position said springbail in response to manual positioning of said control knob to adjustthe depression touch effort of the key levers.

1. An apparatus for adjusting the depression touch effort of key leversin a key lever actuated business machine, comprising: a spring bailmovably mounted in the business machine; key lever spring meansoperatively connected to each key lever and to said spring baileffecting the depression touch effort of the key lever and urging saidspring bail to move in a given direction; counterbalance spring meansoperatively connected to said spring bail for urging said spring bail tomove in a direction opposite to said given direction of said key leverspring means, said counterbalance spring means includes a shaft, amember extending substantially radially from said shaft, and a springconnected to said member, said spring being operable by said member formoving said spring from a position substantially crossing the axis ofsaid shaft to a position away from the axis of said shaft to increasethe pulling force of said spring as said spring decreases in length; andcontrol means operatively connected to said spring bail and to saidcounterbalance spring means for adjusting said key lever spring meansthereby effecting the depression touch effort of the key levers and forsimultaneously adjusting said counterbalance spring means to minimizevariations of the spring forces acting on said control means.
 2. Theapparatus as defined in claim 1 wherein said control means includes alinkage connected to said counterbalance spring means for moving saidspring bail to adjust the depression touch effort of the key leversthrough said counterbalance spring means.
 3. The apparatus as defined inclaim 1 wherein said spring bail is rigidly connected to said shaft ofsaid counterbalance spring means and said spring bail is moved by saidshaft for adjusting the depression touch effort of the key levers. 4.The apparatus as defined in claim 1 wherein said spring bail is rigidlyconnected to said shaft of said counterbalance spring means, said memberof said counterbalance spring means is rigidly connected to said shaftand said control means includes a linkage connected to said member andoperable to move said member for moving said spring bail to adjust thedepression touch effort of the key levers.
 5. The apparatus as definedin claim 1 wherein said control means includes a brake means to resistmovement of said control means, said counterbalance spring means andsaid spring bail from any adjusted position of said control means. 6.The apparatus as defined in claim 5 wherein said control means includesa control knob and said brake means includes a brake member contactingsaid control knob to prevent said control knob from drifting fromadjusted positions.
 7. The apparatus as defined in claim 1 wherein saidcontrol means includes: a control knob rotatably mounted in the businessmachine; a cam surface in said control knob; and pivot means in contactwith said cam surface and operatively connected to said spring bail toposition said spring bail in response to manual positioning of saidcontrol knob to adjust the depression touch effort of the key levers.